class_docstr: Lightweight immutable Dataframe similar to Pandas Dataframe.
code: def columns(self) -> Sequence[Sequence[Any]]:
      return (
          self._columns
          if self._columns
          else [
              [r[i] for r in self._rows]
              for i in range(len(self._rows[0]))
          ]
      )
  
imports: import itertools
  import json
  from typing import Any, Callable, Optional, Sequence, Tuple, Union
  from collections import namedtuple
  import numpy
  from tensorflow.python.compiler.tensorrt.model_tests import model_handler
  import tensorflow.python.compiler.tensorrt.trt_convert
  from tensorflow.python.platform import tf_logging
label_desc: Use image node_id 6 for calling the DataFrame obj's underlying member method code with example usage: obj.columns() and returns: unknown